Complex aluminum greases of enhanced stability



. US. Cl. 252-18 3,514,400 COMPLEX ALUMINUM GREASES OF ENHANCEDSTABILITY Bruce W. Hotten, Orinda, Califi, assignor to Chevron ResearchCompany, San Francisco, Calif., a corporation of Delaware No Drawing.Continuation-impart of application Ser. No. 451,068, Apr. 26, 1965. Thisapplication July 24, 1967, Ser. No. 655,350

Int. Cl. C10m 5/14, 5/12, 5/02 a ,7 .6 Claims ABSTRACT OF THE DISCLOSUREGreases thickened with partially neutralized aluminum mixed carboxylicacid salts having enhanced oxidative and thermal stability, resultingfrom the addition of alkali metal aroates in combination with zincoxide. The greases find particular use for lubricating machineryemployed in the presence of food.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is acontinuation-in-part of application Ser. No. 451,068, filed Apr. 26,1965.

BACKGROUND OF THE INVENTION Field of the invention Lubricants used inmachinery for food processing not only must fulfill their normallubricant function, but also are severely limited to materials approvedby the Food and Drug Administration. Therefore, in preparing greases tobe used in food processing machinery, not only must the thickener beacceptable, but any additives in the grease almost must be acceptable soas not to be possible contaminants in food. Many additives whichordinarily might find use in enhancing the properties of a grease cannotbe used in greases for food processing machinery.

Description of the prior art SUMMARY OF THE INVENTION Oxidative andthermally stabilized aluminum salt thickened greases are providedcomprising an aluminum base partially neutralized with a mixture ofdissimilar carboxylates, namely an aromatic carboxylic acid andoleophilic aliphatic carboxylic acid, and as stabilizers, an alkalimetal aroate and zinc oxide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Basic complex aluminum soap Thealuminum soap thickeners have at least 2 dissimilar substantiallyhydrocarbonaceous organic anions having certain characteristics. One ofthe organo carboxylate anions of the complex soap molecule has a greateroil solubility than the other organic carboxylate anion of the: samesoap molecule. The aluminum di-soaps of the .fnited States Patent 0 icemore soluble organo carboxylate anions (i.e., the relatively oleophilicanions) are soluble in an amount of at least 5% (by volume) at 400 F. inpetroleum white oil having viscosity characteristics of 34-6 SUS at F.and 54 SUS at 210 F. and having a viscosity index of 92. By contrast,the aluminum soaps of the less soluble organic carboxylate anions (i.e.,the relatively oleophobic anions) are soluble in the same white oil inan amount of less than 1% at 400 F.

The carboxylic acids from which the oleophilic anions are derived areillustrated by caprylic acid, capric acid,

lauric acid, myristic acid, palmitic acid, stearic acid, 12-hydroxystearic acid, arachidic acid, melissic acid, oleic acid, linoleicacid, etc. The preferred acids are stearic acid and hydroxystearic acid.The preferred carboxylic acids are the hydrocarbon and hydroxyhydrocarbon carboxylic acids having from 14 to 22 carbon atoms, moreusually from 16 to 18 carbon atoms.

The relatively oleophobic anions are substantially bydrocarbon instructure, are from about 7 to 12 carbon atoms and have an aromatichydrocarbon ring (benzene). Illustrative of such acids are benzoic acid,toluic acid, ethylbenzoic acid, phenylacetic acid, phenylpropionic acid,salicyclic acid, etc. The preferred acids are those of from 7 to 9carbon atoms having the carboxyl group bonded to the benzene ring, e.g.,benzoic acid, toluic acid, dimethylbenzoic acid, and ethylbenzoic acid.

The basic complex aluminum soap may be described by the general formula:

(O- (R'0).A1 o

(O%Ar), in which R is an aliphatic group having 7 to about 29 carbonatoms, Ar is an aromatic hydrocarbon radical, preferably a monocyclichydrocarbon radical, R is either hydrogen or a lower aliphatichydrocarbon radical (1 to 6 carbon atoms), at least one-half of R beinghydrogen, x is at least 0.25, y is at least 0.25, the sum of x and y isfrom 1.5 to 2.5, and z is from 0.5 to 1.5. The aluminum is trivalent inthe above formula and, therefore, the sum of x, y and z is 3. However,this formula is not intended to indicate the actual struture of thealuminum salt in the grease, but rather indicates the stoichiometrybetween the aluminum cation and the anions.

Illustrative of R, which is derived from the lower alcoholates used, aremethyl, ethyl, propyl, isopropyl, butyl, or mixtures thereof.

While any of the methods of preparation disclosed in the various patentsindicated above might be used, a preferred method of preparation isdisclosed in copending application Koundakjian and Dreher, Ser. No.331,127, filed Dec. 17, 1963, now US. Pat. 3,345,291. Accordingly,approximately 1.5 to 2.5 molar parts of the oleophilic acid andoleophobic acid, in which the mole ratio of the oleophilic acid to theoleophobic acid is in the range of from about 0.25:1 to 4:1,approximately 1 molar part of a lower aluminum alcoholate, from 0 to 1.5molar parts of water and a large molar excess of an oil of lubricatingviscosity are heated to a temperature in the range of about to 300 F.,until reaction of the alcoholate with the acids is substantiallycomplete, then a quantity of water is added in the range of 0.05 to 10molar parts, at least sufiicient to bring the total water introduced toat least about 0.5 molar part, and the resultant mixture is vigorouslyagitated at a temperature of from about 200 to 500 F. The grease is thenready to be used.

When preparing the grease, the alkali metal aroate may be added togetherwith the aluminum alcoholate and carboxylic acids or may be subsequentlymilled in with the prepared grease. The other additives will normally beincorporated during the preparation of the grease, conveniently beingadded at the same time as the aluminum alcoholate and carboxylic acids.

Alkali metal aroates Included in the grease is an alkali metal aroate,the alkali metal being of atomic number 3 to 19 and preferably 11(sodium). Said aroate is an alkali metal salt of an aromaticmonocarboxylic acid having 7-12 carbon atoms and having the carboxylcarbon atom bonded to an aromatic ring carbon atom. The preferredaromatic monocarboxylic acid is benzoic acid.

Other materials The alkali metal aroate is generally used in combinationwith zinc oxide. While zinc oxide is normally used as a filler, in thepresent invention when used in combination with an alkali metal aroate,it greatly extends the oxidative and thermal life of the aluminumcomplex salt thickener.

Other materials which are normally present are rust inhibitors,particularly sodium nitrite, and viscosity index improvers.

The oil component of the grease is a hydrocarbon oil of lubricatingviscosity derived from petroleum or synthesized. Description of thevarious oils is found in US. Pat. No. 2,768,138. These oils may be mixedbase, naphthenic base, asphaltic base or parafiin base. The syntheticoils may be derived by the polymerization of ethylene, propylene,isobutylene, or other hydrocarbon olefin to an oil of the desiredviscosity.

to the mixer. The aluminum isopropoxide was added to the mixer over a30-minute period while agitation in the mixer was maintained andcirculation of the mixture through the Charlotte mill was maintained.

The circulation and agitation were continued for minutes, while thetemperature was maintained at 210 to 220 F. At the end of 45 minutes,6.2 pounds of water was added and the resultant mixture was slowlyheated to 320 F. During the heating, the materials in the mixer wereagitated, but circulation through the mill was discontinued. After thetemperature of 320 F. was reached (approximately 1 hour), the reactionmixture was slowly cooled with continuing agitation to 230 F. During thecooling, the remainder of the white oil was added.

When the temperature of 230 F. was reached, the sodium nitrite mixedwith 3 gallons of water was added to the reaction mixture, which wasthen reheated to 260 F., and held at that temperature for about 30minutes to dehydrate the reaction mixture. The reaction mixture was thencooled to 200 F. and the sodium benzoate and the zinc oxide added.

The resultant mixture was circulated through the Charlotte mill andslowly cooled to 160 F. When the temperature reached 160 F., it waswithdrawn from the mixture and passed through a filter screen andpackaged.

Following the procedure of Example I, greases having varying Weightpercents of the aluminum salts were prepared. Also varied was the methodof introduction of the sodium benzoate. These greases were testedaccording to the Thin Film Life Test at 250 F., both in the presence andabsence of other additives. A description of the Thin -Film Life Test isfound in NLGI Spokesman, May 1957, p. 13.

TABLE I Amounts are reported as weight per cent A B C D E F G H I Basegrease A l 100 95 97 92 Base grease B 98 97 93 97 03 Acryloid J17 0. .50. 5 Zinc oxide 2.0 2. 0 2.0 2.0 2.0 2.0 2.0 Sodium nitrite. 0, 5 0. 5Sodium benzoate 6. 5.0 3 1. 0 3 5. 0 4 1.0 4 5.0 Thin film life, hr. at250 F 24 300 24 168 48 120 l, 128 120 1, 128

l 12% aluminum benzoate stearate hydroxide in White Oil having 466 SUSat 100 F. and 62 SUS at 210 F 2 9.2% aluminum benzoate stearatehydroxide in White Oil having 466 SUS at 100 F. and 62 SUS at 3 Sodiumbenzoate milled into the g 4 Sodium benzoate added as water s AMOUNTSThe amount of thickener will generally be in the range of about 4 to 16weight percent, more usually in the range of about 7 to 15 weightpercent of the total composition. The alkali metal aroate will normallybe present in an amount of from 0.1 to 20 weight percent more usuallyfrom 1 to 7 weight percent based on the total composition. The zincoxide will normally be present in amount of about 0.5 to 5 weightpercent, more usually in the range of about 1 to 3 weight percent. Otheradditives which may be present such as sodium nitrite or polymericviscosity index improvers will normally be present in a total amount offrom about 0.1 to 2 weight percent, more usually from about 0.5 to 1.5weight percent. The remainder will be the lubricating oil.

The following example is offered by way of illustration and not by wayof limitation.

EXAMPLE I A 1,600 pound batch of grease was prepared as follows. Thecomponents of the batch were 64.8 pounds of stearic acid, 36.2 pounds ofbenzoic acid, 53.1 pounds of aluminum isopropoxide, 1,320 pounds ofwhite oil, 8 0 pounds of sodium benzoate, 32 pounds of zinc oxide, 8pounds of sodium nitrite and 6.2 pounds of water.

The stearic acid, benzoic acid and 150 gallons of white oil were chargedto a mixer and heated to 220 F. with agitation. After the acids weredissolved, the solution was circulated from the mixer to a Charlottemill and back Base Grease 1 Grease+Additive 2 Penetration worked 311 312Dropping point 487 480 Percent 011 separation:

At 210 F. for 30 hrs. (FTM 6.16 4.02

N 0. 791-321). 6. 65 At ambient temperatures 5. 5.0

for 24 hrs. (ASTM D 1742). 6. 13

7.5% aluminum benzoate stearate 466 SUS at F. and 62 SUS at 210 ?Abo vebase grease plus 1.7% zinc oxide and 3.6% sodium benzoate mllled intothe base grease (the difference in the results is within experimentalerror and can be explained on the basis of the additional milling).

ydroxide in white oil having It is evident from the above tables that agreat extension of useful life is obtained by the addition of sodiumbenzoateas exemplary of alkali metal aroatesto the aluminum complexgreases. Not only is this evident with the sodium benzoate by itself,but when used in combination with zinc oxide, a surprisingly greaterextension of the useful lifetime of the grease is obtained. Moreover,these additives are effective with other additives normally used in thegrease. These additives are particularly effective with'white oil, whichis generally employed for greases to be used in machines in propinquityof food.

As will be evident to those skilled in the art, various modifications onthis invention can be made or followed, in the light of the foregoingdisclosure and discussion, without departing from the spirit or scope ofthe disclosure or from the scope of the following claims.

I claim:

1AA lubricating oil composition comprising an oil of lubricatingviscosity and in an amount sufficient to thicken said oil to a grease, acompound of the formula:

in which R is an aliphatic group having from about 7 to 29 carbon atoms,R is selected from the group consisting of hydrogen and a loweraliphatic hydrocarbon radical, at least one-half of R being hydrogen,and Ar is an aromatic hydrocarbon of from 6 to 11 carbon atoms, x is atleast 0.25, y is at least 0.25, the sum of x and y is from 1.5 to 2.5, zis from 0.5 to 1.5, and the sum of x, y and z is 3, and,

in an amount sufiicient to provide thermal and oxidative stabilization,an alkali metal salt of an aromatic monocarboxylic acid having 7-12carbon atoms and having the car boxyl carbon atom bonded to an aromaticring carbon atom, wherein said? metal is of atomic number 3 to 19, andzinc oxide.

2. A composition according to claim 1, wherein said alkali metal is ofatomic number 11.

3. A composition according to claim 1, wherein said alkali metal ;is ofatomic number 11, said alkali metal salt is present in an amount of fromabout 0.1 to 10 weight percent of said composition, and said zinc oxideis present in an amount of from about 0.5 to weight percent of saidcomposition.

4. A composition according to claim 1, wherein said alkali metal is ofatomic number 11 and said alkali metal salt is present in amount ofabout 5 weight percent of said composition.

5. A lubricating oil composition comprising an oil of lubricatingviscosity and in an amount sufiicient to thicken said oil to a grease, acompound of the formula:

(RO),--Al O (OCAr) in which RCO is 12-hydroxystearoyloxy, ArCO isbenzoyloxy, R is selected from the group consisting of hydrogen andmethoxy, at least one-half of R being hydrogen, x is at least 0.25, y isat least 0.25, the sum of x and y is from 1.5 to 2.5, z is from 0.5 to1.5 and the sum of x, y and z is 3, and

in an amount sufficient to provide thermal and oxidative stabilization,sodium benzoate and zinc oxide.

6. A composition according to claim 5, wherein said sodium benzoate ispresent in an amount of from about 5 weight percent of said compositionand said zinc oxide is present in from about 1 to 3 weight percent.

References Cited UNITED STATES PATENTS 2,043,638 6/1936 Watts 252-112,182,137 12/1939 Ricketts 2524l 2,599,553 6/1952 Hotten 25237.72,671,758 3/1954 Vinograd et al. 252-48 2,860,104 11/ 1958 Peterson etal 25228 OTHER REFERENCES Manufacture and Application of LubricatingGreases by Boner, Reinhold Pub. Corp., New York, 1954, p. 781.

DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner US. Cl.X.R. 25225, 400

